NativeWeb
From the web site, it contains "an extensive listing of resources for Indigenous people and nations  around the world."  Other sections include Books and Music ("Hundreds of Books, Cassettes and CD's, categorized and linked to Amazon.com"), Hosted Materials ("Links to the main pages hosted on NativeWeb"), Abya Yala Net ("Information on Indigenous peoples in Mexico, Central, and South America"), and Communities, ("Message boards, white pages, jobs, events and more").

Lisa Mitten's Page of Native American Web Sites
Use this award-winning page to find an extensive collection of Native American links from Lisa Mitten at the University of Pittsburgh.

Karen Strom's Index of Native American Resources on the Internet
Use this page to find another extensive collection of Native American links, collected by Karen Strom.

Dee Finney's Native American Culture Page
Here's another huge collection of Native American links.  All of the links are on one page, so be patient while this 350K+ file loads.

First Nations Website
Here's a large collection of First Nations links.  From Canada's SchoolNet. 

NAPE Aboriginal Links: An Indigenous People's Web Directory 
From the web site, this is "a comprehensive web directory presenting categorized information to Canadian Aboriginal, Native American Indian and International Indigenous sites on the world wide web."

Lakota na Dakota Wowapi Oti Kin (Lakota Dakota Information Home Page)
From the web site, this site contains a large collection of links and "is a joint project by Martin Broken Leg at Augustana College, Sioux Falls, SD,  and Raymond Bucko, S.J. at Le Moyne College, Syracuse, NY. This page deals with Lakota and Dakota peoples. These distinct but related groups are sometimes referred to as Sioux or Siouan peoples. This page does not represent an officially sanctioned voice for any of these peoples either as individuals or as corporate groups." 

Lakota Sioux
From the web site, this page includes a listing of Sioux links in South Dakota, organized into the following topics: "Introductions; Historical; Tribes; Legends & Spiritual; Pictures; Points of Interest; Organizations; Art, Music, & Dance; Language; Political; Movies; Individuals; Maps & Data; Black Hills Shops; Media."  Part of the Black Hills Information Web web site.